Semiconductor laser module

ABSTRACT

A semiconductor laser module that includes a package accommodating therein a plurality of optical components, includes: a semiconductor laser device that emits laser light toward one end side in the package; an optical fiber having an incident end of the laser light on another end side in the package, the another end being in an opposite direction of an emission direction in which the semiconductor laser device emits the laser light; and a turn-back unit that turns back the laser light toward the another end side in the package, the another end being in the opposite direction of the emission direction in which the semiconductor laser device emits the laser light, and outputs the laser light to the incident end of the optical fiber.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Application No.PCT/JP2019/005457, filed on Feb. 14, 2019 which claims the benefit ofpriority of the prior Japanese Patent Application No. 2018-024398, filedon Feb. 14, 2018, the entire contents of which are incorporated hereinby reference.

BACKGROUND

The present disclosure relates to a semiconductor laser module.

In general, it is known that semiconductor laser modules have structuresin which a plurality of optical components such as semiconductor laserdevices are housed in their packages (e.g., refer to Japanese Laid-openPatent Publication No. 2005-99166).

SUMMARY

There is a need for providing a semiconductor laser module capable ofdownsizing the package in the long side direction.

According to an embodiment, a semiconductor laser module that includes apackage accommodating therein a plurality of optical components,includes: a semiconductor laser device that emits laser light toward oneend side in the package; an optical fiber having an incident end of thelaser light on another end side in the package, the another end being inan opposite direction of an emission direction in which thesemiconductor laser device emits the laser light; and a turn-back unitthat turns back the laser light toward the another end side in thepackage, the another end being in the opposite direction of the emissiondirection in which the semiconductor laser device emits the laser light,and outputs the laser light to the incident end of the optical fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view schematically illustrating a structure of asemiconductor laser module according to a first embodiment;

FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1;

FIG. 3 is a plan view schematically illustrating a structure of asemiconductor laser module according to a second embodiment;

FIG. 4 is a plan view of a lid portion according to a first modificationof the first and the second embodiments;

FIG. 5 is a plan view of a lid portion according to a secondmodification of the first and the second embodiments;

FIG. 6 is a plan view of a lid portion according to a third modificationof the first and the second embodiments;

FIG. 7 is a plan view of a lid portion according to a fourthmodification of the first and the second embodiments;

FIG. 8 is a plan view schematically illustrating a structure of asemiconductor laser module according to a fifth modification of thefirst and the second embodiments;

FIG. 9 is a plan view schematically illustrating a structure of asemiconductor laser module according to a sixth modification of thefirst and the second embodiments;

FIG. 10 is a plan view schematically illustrating a structure of asemiconductor laser module according to a seventh modification of thefirst and the second embodiments;

FIG. 11 is a plan view schematically illustrating a structure of asemiconductor laser module according to an eighth modification of thefirst and the second embodiments;

FIG. 12 is a plan view schematically illustrating a structure of asemiconductor laser module according to a ninth modification of thefirst and the second embodiments;

FIG. 13 is a plan view schematically illustrating a structure of asemiconductor laser module according to a tenth modification of thefirst and the second embodiments; and

FIG. 14 is a cross-sectional view taken along line B-B in FIG. 13.

DETAILED DESCRIPTION

In the related art, with an increase in number of optical components inthe semiconductor laser modules, their package sizes in their long sidedirections increase. A problem, however, arises in that the packageneeds to be downsized as a conflicting request.

The following describes embodiments with reference to the accompanyingdrawings. The embodiments do not limit the present disclosure. Elementsidentical or corresponding to each other are provided with the samenumeral appropriately in the respective drawings, and duplicateddescriptions thereof are appropriately omitted. The drawings areschematic and attention needs to be paid that dimensional relationsamong the elements and ratios among the elements differ from those ofactual ones in some cases, for example. Among the drawings, thedimensional relations and ratios among the elements also differ in somecases.

First Embodiment

Semiconductor Laser Module

FIG. 1 is a plan view schematically illustrating a structure of asemiconductor laser module according to a first embodiment. FIG. 2 is across-sectional view taken along line A-A in FIG. 1.

This semiconductor laser module 1 illustrated in FIGS. 1 and 2 includesa package 2, a temperature regulator 3, a laser support member 4, whichis also called a sub-mount, a semiconductor laser device 5, acollimating lens 6, a beam splitter 7, a mirror 8, an optical isolator9, a condenser lens 10, an optical fiber 11, a fiber holder 12, a photodiode 13 (hereinafter, simply described as a “PD 13”), a coupling lens14, a wavelength detection element 15, a photo diode 16 (hereinafter,simply described as a “PD 16”), a photo diode 17 (hereinafter, simplydescribed as a “PD 17”), a support member 18, which is called a base,and a lid portion 19. FIGS. 1 and 2 illustrate the package 2 and the lidportion 19 in parallel with each other in a state where the lid portion19 is removed from the package 2 for explaining an internal structure ofthe semiconductor laser module 1. The temperature regulator 3 and thesupport member 18 have substantially the same size when they are viewedfrom above. The temperature regulator 3 is, thus, not seen in FIG. 1.

The package 2 has a rectangular shape in a plan view and a side view.The package 2 houses therein the temperature regulator 3, the lasersupport member 4, the semiconductor laser device 5, the collimating lens6, the beam splitter 7, the mirror 8, the optical isolator 9, thecondenser lens 10, the optical fiber 11, the fiber holder 12, the PD 13,the coupling lens 14, the wavelength detection element 15, the PD 16,and the PD 17.

The temperature regulator 3 regulates respective temperatures of thesemiconductor laser device 5 placed on the laser support member 4 andthe wavelength detection element 15 in accordance with driving currentssupplied from a controller (not illustrated) via electrodes (notillustrated). The temperature regulator 3 has a structure in which aplurality of columnar semiconductor devices (N type and P typesemiconductor devices) stand vertically and are arrangedtwo-dimensionally between substrates. In the temperature regulator 3,the upper ends and the lower ends of the respective N-type and P-typesemiconductor devices are connected to the lower and the uppersubstrates by metallic electrodes, and the N-type and P-typesemiconductor devices are alternately connected in series. Thesemiconductor devices are formed using BiTe, for example.

The laser support member 4 is provided on the upper surface of thesupport member 18. On the upper surface of the laser support member 4,the semiconductor laser device 5 is placed. The laser support member 4is formed using a material such as aluminum oxide, aluminum nitride,copper tungsten, silicon carbide, silicon, copper, or diamond. The lasersupport member 4 is more preferably formed using a material having ahigh thermal conductivity.

The semiconductor laser device 5 emits laser light L1 toward one endside in the package 2. The semiconductor laser device 5 emits the laserlight L1 and laser light L2 in accordance with driving currents suppliedfrom the controller (not illustrated). In the first embodiment, the sidetoward which the semiconductor laser device 5 emits the laser light L1is described as a rear side while the side toward which thesemiconductor laser device 5 emits the laser light L2 is described as afront side in the package 2.

The collimating lens 6 collimates the laser light L1 emitted from thesemiconductor laser device 5 and outputs the collimated laser light L1to the beam splitter 7.

The beam splitter 7 allows part of the laser light L1 collimated by thecollimating lens 6 to pass therethrough to the PD 13 while the beamsplitter 7 reflects the rest of laser light L1 to the mirror 8.

The mirror 8 reflects the laser light L1 reflected by the beam splitter7 to the optical isolator 9.

The optical isolator 9 is bonded to the upper surface of the supportmember 18 with an adhesive (not illustrated) or resin, for example. Theoptical isolator 9 includes a permanent magnet. The optical isolator 9allows the laser light L1 reflected by the mirror 8 to pass therethroughto the condenser lens 10 while the optical isolator 9 blocks lightentering from the condenser lens 10 side. The optical isolator 9 isformed such that an optical axis shift of the laser light L1 caused bythe optical isolator 9 and a refraction direction of the laser light L1caused by the condenser lens 10 are opposite to each other.Specifically, an incident end face, on which the laser light L1 isincident, of the optical isolator 9 is formed such that the incident endface is tilted with respect to the laser light L1. The permanent magnetof the optical isolator 9 is made of a material such as samarium cobalt,neodymium, or ferrite.

The condenser lens 10 condenses the laser light L1 having passed throughthe optical isolator 9 to couple the laser light L1 to the optical fiber11. In the first embodiment, the structure including the collimatinglens 6, the beam splitter 7, the mirror 8, the optical isolator 9, andthe condenser lens 10 functions as a turn-back unit that turns back thelaser light L1 toward the other end side in the package 2 in theopposite direction of the emission direction in which the semiconductorlaser device 5 emits the laser light L1, and emits the laser light L1 tothe incident end of the optical fiber 11.

The optical fiber 11 is provided in the package 2 in such a manner thatthe incident end on which the laser light L1 is incident faces the otherend side in the package 2 that is in the opposite direction of theemission direction in which the semiconductor laser device 5 emits thelaser light L1. The optical fiber 11 is provided by being inserted inthe package 2. The optical fiber 11 propagates the laser light L1coupled thereto by the condenser lens 10. The fiber holder 12 holds theoptical fiber 11.

The PD 13 receives the laser light L1 having passed through the beamsplitter 7 and outputs a current signal according to the receivedoptical power to the controller (not illustrated). The controller (notillustrated) controls the driving current supplied to the semiconductorlaser device 5 on the basis of the current signal received from the PD13. For example, the controller (not illustrated) controls the drivingcurrent supplied to the semiconductor laser device 5 such that thecurrent signal received from the PD 13 maintains a fixed value. As aresult, the controller (not illustrated) can control the optical outputof the semiconductor laser device 5 constant.

The coupling lens 14 is placed on the upper surface of the temperatureregulator 3 on the front side opposite to the emission side toward whichthe semiconductor laser device 5 emits the laser light L1 in the package2. The coupling lens 14 couples the laser light L2 output from thesemiconductor laser device 5 to the wavelength detection element 15.

The wavelength detection element 15 includes at least a light branchingsection (not illustrated) and a filter section (not illustrated). Thelight branching section branches the laser light L2 and inputs onebranched laser light to the PD 16. The filter section, which has atransmission characteristic at periodic light frequency, transmits theother branched laser light branched by the light branching section andinputs the laser light after transmission to the PD 17.

Each of the PDs 16 and 17 receives the corresponding laser light andoutputs a current signal according to the received optical power to thecontroller (not illustrated). The controller (not illustrated) controlsthe driving current supplied to the temperature regulator 3 on the basisof the current signals received from the PDs 16 and 17. As a result, thecontroller adjusts the temperature of the semiconductor laser device 5to control the wavelength of the laser light L1 output by thesemiconductor laser device 5. Such control is a known technique calledwavelength locking. The wavelength detection element 15 can be achievedby an optical waveguide element such as a planar lightwave circuit (PLC)or a space coupling system. The filter section can be achieved by a ringfilter or an etalon filter, for example. When the wavelength detectionelement 15 is achieved by the space coupling system, for example, thecoupling lens 14 is replaced with a collimating lens.

The support member 18 is provided on the upper surface of thetemperature regulator 3. On the upper surface of the support member 18,the laser support member 4, the collimating lens 6, the beam splitter 7,the mirror 8, the optical isolator 9, the condenser lens 10, the fiberholder 12, the PD 13, the coupling lens 14, the wavelength detectionelement 15, the PD 16, and the PD 17 are placed. The support member 18is formed using a material such as aluminum oxide, aluminum nitride,copper tungsten, silicon carbide, silicon, copper, or diamond. Thesupport member 18 is more preferably formed using a material having ahigh thermal conductivity.

The lid portion 19, which has a rectangular shape, is mounted on thepackage 2 and hermetically sealed. The lid portion 19 has a main bodyportion 191 that is in contact with the upper end portion of a sidewall21 of the package 2 when the lid portion 19 is mounted on the package 2,and a thick portion 192 that is provided on a lower surface side of themain body portion 191. In FIGS. 1 and 2, the two portions denoted as 192are the thick portion 192 as a whole. The thick portion can increase astrength of the lid portion 19 and can be used as a positioning portionthat determines the position of the lid portion 19 with respect to thepackage 2. The main body portion 191 and the thick portion 192 areformed integrally. The main body portion 191 and the thick portions 192are formed integrally using Kovar, for example.

The thick portion 192 is formed such that the length in a short sidedirection and the length in a long side direction of the thick portion192 are shorter than that in the short side direction and that in thelong side direction of the main body portion 191, respectively. Thethick portion 192 is formed such that the length in the short sidedirection and the length in the long side direction of the thick portion192 are substantially the same as that in the short side direction andthat in the long side direction on the inner side of the sidewall 21 ofthe package 2, respectively. As illustrated in FIGS. 1 and 2, the thickportion 192 is provided on the lower surface side other than a lowersurface region R1 of the main body portion 191, the lower surface regionR1 being directly above the optical isolator 9 housed in the package 2.Specifically, regarding the thick portion 192, when the lid portion 19is mounted on the package 2, the shortest distance D1 from the uppersurface of the optical isolator 9 to the lower surface of the thickportion 192 is equal to or larger than 0.8 mm. In addition, the thickportion 192 is formed such that a normal line distance X1 satisfies 0.8mm≤X1 mm≤T1 mm+0.8 mm where the thick portion 192 has a thickness of T1mm and the normal line distance from the lower surface of the lidportion 19 to the upper surface of the optical isolator 9 is X1 mm. Thethick portion 192 determines the position of the lid portion 19 by beingin contact with the inner surface side of the sidewall 21 in the package2 when the lid portion 19 is mounted on the package 2. This structureallows the optical isolator 9 to make the magnetic force strengthsmaller than the adhesive strength of the adhesive, thereby preventingthe optical isolator 9 from sticking to the lid portion 19. As a result,the optical isolator 9 is reliably prevented from being separated fromthe support member 18.

The first embodiment thus described above can downsize the package 2 inthe long side direction.

In the first embodiment, the optical isolator 9 is formed such that thelight axis shift of the laser light L1 and the refraction direction ofthe laser light L1 caused by the condenser lens 10 are opposite to eachother. As a result, the first embodiment can prevent an increase in sizeof the package 2 in the long side direction.

In the first embodiment, the wavelength detection element 15 is disposedon the other end side opposite to the emission end from which thesemiconductor laser device 5 emits the laser light L1, and thesemiconductor laser device 5 is disposed such that the rear end surfaceof the semiconductor laser device 5 is further on the inner side of thepackage 2 than the front end surface of the semiconductor laser device5. As a result, this structure makes it possible to dispose thesemiconductor laser device 5 serving as a heat generation source at thecenter in the package 2 in both directions parallel to and perpendicularto the insertion direction of the optical fiber 11, thereby allowing thetemperature regulator 3 to more efficiently take in heat than a casewhere the heat generation source is disposed on the end of the package2. Consequently, the first embodiment can reduce power consumption.

In the first embodiment, the thick portion 192 is disposed on the lowersurface side other than the lower surface region R1 of the main bodyportion 191, the lower surface region R1 being directly above theoptical isolator 9. This structure can prevent the optical isolator 9from being separated from the support member 18.

Second Embodiment

The following describes a second embodiment. In the first embodiment,laser light is guided from the semiconductor laser device 5 to theincident end of the optical fiber 11 by being turned back in asubstantially U-shape. In the second embodiment, laser light is guidedin a substantially V-shape. In the following description, the samestructure as that in the first embodiment is labeled with the samenumeral and detailed description thereof is omitted.

Semiconductor Laser Module

FIG. 3 is a plan view schematically illustrating a structure of asemiconductor laser module according to the second embodiment. In asemiconductor laser module 1A illustrated in FIG. 3 differs from thefirst embodiment in that the beam splitter 7 is omitted, and the mirror8 is changed to a beam splitter 8A. Specifically, the semiconductorlaser module 1A includes the package 2, the temperature regulator 3, thelaser support member 4, a semiconductor laser device 5A, a collimatinglens 6A, the beam splitter 8A, the optical isolator 9, the condenserlens 10, the optical fiber 11, the fiber holder 12, the PD 13, thecoupling lens 14, the wavelength detection element 15, the PD 16, the PD17, and the support member 18. The package 2 is provided with the lidportion 19 (not illustrated) in the first embodiment. The semiconductorlaser module 1A is illustrated in a state where the lid portion 19 isremoved for explaining the internal structure of the semiconductor lasermodule 1A.

The semiconductor laser device 5A, which is on one end side in thepackage 2, emits the laser light L1 toward the collimating lens 6A. Thesemiconductor laser device 5A outputs the laser light L1 and laser lightL2 in accordance with the driving currents supplied from the controller(not illustrated).

The collimating lens 6A is disposed on an optical path of the laserlight L1 between the semiconductor laser device 5A and the beam splitter8A. The collimating lens 6A collimates the laser light L1 output fromthe semiconductor laser device 5A and outputs the collimated laser lightL1 to the beam splitter 8A.

The beam splitter 8A allows part of the laser light L1 collimated by thecollimating lens 6A to pass therethrough to the PD 13 while the beamsplitter 8A reflects the laser light L1 to the optical isolator 9.

The second embodiment thus described above has the same effect as thefirst embodiment and can omit the mirror 8 included in the firstembodiment, thereby making it possible to achieve lower cost than thefirst embodiment.

First Modification of First and Second Embodiments

The following describes a first modification of the first and the secondembodiments. In the first modification of the first and the secondembodiments, a lid portion has a different structure from that of thelid portion 19 according to the first and the second embodiments. Thefollowing describes only the lid portion according to the firstmodification of the first and the second embodiments.

FIG. 4 is a plan view of the lid portion according to the firstmodification of the first and the second embodiments when viewed fromthe rear side. A lid portion 19B illustrated in FIG. 4 has a thickportion 192B instead of the thick portion 192 according to the firstembodiment. The thick portion 192B is provided on the lower surface sideother than the lower surface region R1 of the main body portion 191, thelower surface region R1 being directly above the optical isolator 9housed in the package 2. The thick portion 192B is formed such that thethick portion 192B is in contact with an inner side of the sidewall 21of the package 2 at at least four corners of the sidewall 21.

The first modification of the first and the second embodiments thusdescribed above can prevent the optical isolator 9 from being separatedfrom the support member 18.

Second Modification of First and Second Embodiments

The following describes a second modification of the first and thesecond embodiments. In the second modification of the first and thesecond embodiments, a lid portion has a different structure from that ofthe lid portion 19 according to the first and the second embodiments.The following describes only the lid portion according to the secondmodification of the first and the second embodiments.

FIG. 5 is a plan view of the lid portion according to the secondmodification of the first and the second embodiments when viewed fromthe rear side. A lid portion 19C illustrated in FIG. 5 has a thickportion 192C instead of the thick portion 192 according to the firstembodiment. The thick portion 192C is provided on the lower surface sideother than the lower surface region R1 of the main body portion 191, thelower surface region R1 being directly above the optical isolator 9housed in the package 2. The thick portion 192C is formed such that thethick portion 192C is in contact with the inner side of the sidewall 21of the package 2 at at least three or more corners of the four cornersof the sidewall 21.

The second modification of the first and the second embodiments thusdescribed above can prevent the optical isolator 9 from being separatedfrom the support member 18.

Third Modification of First and Second Embodiments

The following describes a third modification of the first and the secondembodiments. In the third modification of the first and the secondembodiments, a lid portion has a different structure from that of thelid portion 19 according to the first and the second embodiments. Thefollowing describes only the lid portion according to the thirdmodification of the first and the second embodiments.

FIG. 6 is a plan view of the lid portion according to the thirdmodification of the first and the second embodiments when viewed fromthe rear side. A lid portion 19D illustrated in FIG. 6 has a thickportion 192D instead of the thick portion 192 according to the firstembodiment. In FIG. 6, four portions denoted as 192D are the thickportion 192D as a whole. The thick portion 192D is provided on the lowersurface side other than the lower surface region R1 of the main bodyportion 191, the lower surface region R1 being directly above theoptical isolator 9 housed in the package 2. The thick portion 192D has aplurality of protrusions 193 that are formed on the main body portion191 and are in contact with the inner side of the sidewall 21 of thepackage 2 at at least the four corners of the sidewall 21. Theprotrusions 193 are formed on the main body portion 191 such that theyare apart from one another.

The third modification of the first and the second embodiments thusdescribed above can prevent the optical isolator 9 from being separatedfrom the support member 18.

Fourth Modification of First and Second Embodiments

The following describes a fourth modification of the first and thesecond embodiments. In the fourth modification of the first and thesecond embodiments, a lid portion has a different structure from that ofthe lid portion 19 according to the first and the second embodiments.The following describes only the lid portion according to the fourthmodification of the first and the second embodiments.

FIG. 7 is a plan view of the lid portion according to the fourthmodification of the first and the second embodiments when viewed fromthe rear side. A lid portion 19E illustrated in FIG. 7 has a thickportion 192C instead of the thick portion 192 according to the firstembodiment. The thick portion 192E is provided on the lower surface sideother than the lower surface region R1 of the main body portion 191, thelower surface region R1 being directly above the optical isolator 9housed in the package 2. The thick portion 192E is formed in such anannular shape that the thick portion 192E is in contact with the innerside of the sidewall 21 of the package 2 at at least the four corners ofthe sidewall 21.

The fourth modification of the first and the second embodiments thusdescribed above can prevent the optical isolator 9 from being separatedfrom the support member 18.

Fifth Modification of First and Second Embodiments

The following describes a fifth modification of the first and the secondembodiments. FIG. 8 is a plan view schematically illustrating astructure of a semiconductor laser module according to the fifthmodification of the first and the second embodiments. A semiconductorlaser module 1F illustrated in FIG. 8 includes a beam splitter 8F and amirror 7F instead of the beam splitter 7 and the mirror 8 in the firstembodiment, respectively. In addition, the position of the PD 13 in thesemiconductor laser module 1F differs from that of the PD 13 in thefirst embodiment. Specifically, the mirror 7F reflects the laser lightL1 collimated by the collimating lens 6 to the beam splitter 8F. Thebeam splitter 8F allows part of the laser light L1 reflected by themirror 7F to pass therethrough to the PD 13, and reflects the other partof the laser light L1 to the optical isolator 9.

The fifth modification of the first and the second embodiments thusdescribed above can downsize the package 2 in the long side direction.

Sixth Modification of First and Second Embodiments

The following describes a sixth modification of the first and the secondembodiments. FIG. 9 is a plan view schematically illustrating astructure of a semiconductor laser module according to the sixthmodification of the first and the second embodiments. A semiconductorlaser module 1G illustrated in FIG. 9 differs from the structure of thefifth modification of the first and the second embodiments in that themirror 8 is included instead of the beam splitter 8F. The semiconductorlaser module 1G further includes a beam splitter 20 that is disposed onthe optical path between the optical isolator 9 and the condenser lens10. In addition, in the semiconductor laser module 1G, the positions ofthe coupling lens 14, the wavelength detection element 15, the PD 16,and the PD 17 differ from those in the fifth modification of the firstand the second embodiments. Specifically, the beam splitter 20 reflectspart of the laser light L1 having passed through the optical isolator 9to the coupling lens 14, and allows the other part of the laser light L1to pass therethrough to the condenser lens 10.

The sixth modification of the first and the second embodiments thusdescribed above can downsize the package 2 in the long side direction.

Seventh Modification of First and Second Embodiments

The following describes a seventh modification of the first and thesecond embodiments. FIG. 10 is a plan view schematically illustrating astructure of a semiconductor laser module according to the seventhmodification of the first and the second embodiments. A semiconductorlaser module 1H illustrated in FIG. 10 includes the optical isolator 9disposed at a different position from that of the optical isolator 9 inthe first embodiment. Specifically, as illustrated in FIG. 10, theoptical isolator 9 is disposed on the optical path between thecollimating lens 6 and the beam splitter 7.

The seventh modification of the first and the second embodiments thusdescribed above can downsize the package 2 in the long side direction.

Eighth Modification of First and Second Embodiments

The following describes an eighth modification of the first and thesecond embodiments. FIG. 11 is a plan view schematically illustrating astructure of a semiconductor laser module according to the eighthmodification of the first and the second embodiments. A semiconductorlaser module 1I illustrated in FIG. 11 includes the optical isolator 9disposed at a different position from that of the optical isolator 9 inthe first embodiment. Specifically, as illustrated in FIG. 11, theoptical isolator 9 is disposed on the optical path between the beamsplitter 7 and the mirror 8.

The eighth modification of the first and the second embodiments thusdescribed above can downsize the package 2 in the long side direction.

Ninth Modification of First and Second Embodiments

The following describes a ninth modification of the first and the secondembodiments. FIG. 12 is a plan view schematically illustrating astructure of a semiconductor laser module according to a ninthmodification of the first and the second embodiments. A semiconductorlaser module 1J illustrated in FIG. 12 includes the optical isolator 9disposed at a different position from that of the optical isolator 9 inthe first embodiment. Specifically, as illustrated in FIG. 12, theoptical isolator 9 is disposed on the optical path between the condenserlens 10 and the optical fiber 11.

The ninth modification of the first and the second embodiments thusdescribed above can downsize the package 2 in the long side direction.

Tenth Modification of First and Second Embodiments

The following describes a tenth modification of the first and the secondembodiments. In the tenth modification of the first and the secondembodiments, a lid portion has a different structure from that of thelid portion 19 according to the first and the second embodiments. Thefollowing describes only the lid portion according to the tenthmodification of the first and the second embodiments.

FIG. 13 is a plan view that schematically illustrates a structure of asemiconductor laser module according to the tenth modification of thefirst and the second embodiments, and illustrates the lid portion whenviewed from the rear side. FIG. 14 is a cross-sectional viewschematically illustrating a major part of the semiconductor lasermodule according to the tenth modification of the first and the secondembodiments. This semiconductor laser module 1K illustrated in FIGS. 13and 14 includes a lid portion 19K instead of the lid portion 19 of thesemiconductor laser module 1 according to the first embodiment.

The lid portion 19K illustrated in FIGS. 13 and 14 has the main bodyportion 191, a thick portion 192K, and a region portion 194 formed inthe main body portion 191. In FIGS. 13 and 14, the two portions denotedas 192K are the thick portion 192K as a whole. The region portion 194 isformed in a region of the main body portion 191 corresponding to thelower surface region R1, that is directly above the optical isolator 9housed in the package 2, and at least a part of which has no thickportion 192K. The region portion 194 is formed of a material that is notattracted by magnets. Specifically, the region portion 194 is formed ofa material such as glass or ceramics and formed integrally with the mainbody portion 191. The region portion 194 may be formed of metal that isnot attracted by magnets. Examples of such metal include aluminum,copper, manganese, austenitic stainless steel (e.g., SUS 304), andbrass.

The thick portion 192K is formed such that, when the lid portion 19K ismounted on the package 2, the shortest distance D2 from the opticalisolator 9 to the thick portion 192K is equal to or larger than 0.8 mm,and a normal line distance X2 satisfies 0 mm≤X2 mm≤T2 mm+0.8 mm wherethe thick portion 192K has a thickness of T2 mm and the normal linedistance from the lower surface of the lid portion 19K to the uppersurface of the optical isolator 9 is X2 mm. When the thick portion 192Kis formed as described above and the shortest distance D3 between thelid portion 19K outside the region portion 194 and the optical isolatoris equal to or larger than 0.8 mm, the optical isolator 9 can make themagnetic strength smaller than the adhesive strength of the adhesive. Asa result, the optical isolator 9 is prevented from sticking to the lidportion 19K. As a result, the optical isolator 9 is reliably preventedfrom being separated from the support member 18.

The tenth modification of the first and the second embodiments thusdescribed above can prevent the optical isolator 9 from being separatedfrom the support member 18.

The tenth modification of the first and the second embodiments allowsthe respective shapes of the thick portions 192B, 192C, 192D, and 192Ein the first to the fourth modifications of the first and the secondembodiments to be applied to the shape of thick portion 192K.

Other Embodiments

In the respective embodiments, the optical fiber 11 is disposed on onesidewall side in the short side direction of the package 2 apart fromthe center of the package 2 in the short side direction. This structuremakes it possible to downsize the module in the long side directionwithout increasing in size of the module in the short side direction.

The present disclosure has an advantageous effect of capable ofdownsizing the package in the long side direction.

Although the disclosure has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. A semiconductor laser module that includes apackage accommodating therein a plurality of optical components, thesemiconductor laser module comprising: a semiconductor laser device thatemits laser light toward one end side in the package; an optical fiberhaving an incident end of the laser light on another end side in thepackage, the another end being in an opposite direction of an emissiondirection in which the semiconductor laser device emits the laser light;and a turn-back unit that turns back the laser light toward the anotherend side in the package, the another end being in the opposite directionof the emission direction in which the semiconductor laser device emitsthe laser light, and outputs the laser light to the incident end of theoptical fiber.
 2. The semiconductor laser module according to claim 1,wherein the turn-back unit includes one or more reflection members. 3.The semiconductor laser module according to claim 2, wherein theturn-back unit further includes: a collimating lens that collimates thelaser light emitted by the semiconductor laser device and emits thecollimated laser light to the reflection member; and a condenser lensthat condenses the laser light reflected by the reflection member to theincident end of the optical fiber.
 4. The semiconductor laser moduleaccording to claim 3, wherein the turn-back unit further includes anoptical isolator that is disposed between the reflection member and thecondenser lens.
 5. The semiconductor laser module according to claim 4,wherein an optical axis shift direction of the laser light caused by theoptical isolator and a refraction direction of the laser light caused bythe condenser lens are opposite to each other.
 6. The semiconductorlaser module according to claim 1, further comprising a wavelengthdetection element that is disposed on the another end side, which isopposite to an emission side from which the semiconductor laser deviceemits the laser light, and detects a wavelength of the laser light. 7.The semiconductor laser module according to claim 1, wherein the opticalfiber is inserted and provided in the package.
 8. The semiconductorlaser module according to claim 1, further comprising a power monitorthat receives the laser light and detects power of the received laserlight, wherein the turn-back unit includes a reflection member thatallows part of the laser to pass therethrough and reflects a rest of thelaser light, and the power monitor is disposed at a position where thelaser light after passing through the reflection member passes throughwhile a light receiving surface of the power monitor faces the position.9. The semiconductor laser module according to claim 1, furthercomprising a power monitor that receives the laser light and detectspower of the received laser light, wherein the turn-back unit includes:a first reflection member that reflects the laser light; a secondreflection member that reflects the laser light reflected by the firstreflection member to the incident end of the optical fiber; and a lightbranching unit that allows part of the laser light reflected by thesecond reflection member to pass therethrough and reflects a rest of thelaser light; and the power monitor is disposed at a position where thelaser light reflected by the light branching unit passes through while alight receiving surface of the power monitor faces the position.
 10. Thesemiconductor laser module according to claim 2, wherein the turn-backunit further includes: a collimating lens that collimates the laserlight emitted by the semiconductor laser device, and emits thecollimated laser light to the reflection member; and an optical isolatorthat is disposed between the reflection member and the collimating lens.11. The semiconductor laser module according to claim 1, wherein theturn-back unit further includes: a first reflection member that reflectsthe laser light; a second reflection member that reflects the laserlight reflected by the first reflection member to the incident end ofthe optical fiber; and an optical isolator that is disposed between thefirst reflection member and the second reflection member.
 12. Thesemiconductor laser module according to claim 2, wherein the turn-backunit further includes: a collimating lens that collimates the laserlight emitted by the semiconductor laser device, and emits thecollimated laser light to the reflection member; a condenser lens thatcondenses the laser light reflected by the reflection member to theincident end of the optical fiber; and an optical isolator that isdisposed between the condenser lens and the incident end of the opticalfiber.
 13. The semiconductor laser module according to claim 4, furthercomprising a lid portion mounted on the package, wherein the lid portionincludes: a main body portion that is in contact with an upper endportion of a sidewall of the package; and a thick portion that isprovided on a lower surface of the main body portion and determines aposition of the lid portion with respect to the package, and the thickportion is provided on the lower surface other than a lower surfaceregion of the main body portion, the lower surface region being directlyabove the optical isolator housed in the package, when the lid portionis mounted on the package.
 14. The semiconductor laser module accordingto claim 13, wherein the thick portion is formed such that the thickportion is in contact with an inner side of the sidewall of the packageat two or more portions of the sidewall.
 15. The semiconductor lasermodule according to claim 1, wherein the optical fiber is disposed onone sidewall side in a short side direction of the package apart from acenter of the package in the short side direction.